


Continuation

by Kamari333



Series: Resonation [3]
Category: Undertale (Video Game)
Genre: Begging, Biting, Collars, Dirty Talk, Ecto-Genitalia (Undertale), Emotions, Empathy, Established Relationship, Idiots in Love, M/M, Orgasm Control, Pet Names, Scent Kink, Sex Games, Soul Sex, The Significance of Collars in Fell-verse culture, Underfell Sans (Undertale), Underfell Sans/Underlust Sans (Undertale), Underlust Sans (Undertale), Valentine's Day
Language: English
Status: Completed
Published: 2020-02-17
Updated: 2020-02-17
Packaged: 2021-02-28 06:53:35
Rating: Explicit
Warnings: No Archive Warnings Apply
Chapters: 1
Words: 3,695
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/22769614
Author URL: https://archiveofourown.org/users/Kamari333/pseuds/Kamari333
Summary: It has been over a year since Lust found his boyfriend in another universe.And today was Valentines Day.
Relationships: Sans/Sans (Undertale)
Series: Resonation [3]
Series URL: https://archiveofourown.org/series/755550
Comments: 32
Kudos: 93





	Continuation

**Author's Note:**

> NO BETA WE DIE LIKE MNE
> 
> its been ages since I wrote these two bastard idiots being gross and slimy and in love despite their many many issues. Resonance-Rust is still great, but its nice to see how its changed over time.
> 
> Lust has always taken his relationships very very seriously.  
> Red has never been good with communication.
> 
> But they keep trying. and thats beautiful.
> 
> have some garbage that made me cry writing it. and happy (late) valentines day.

Its Valentine's Day: thats what Afterrus had told them when he invited everyone back to his home in Aftertale.

Lust let out a soft, breathless noise (that he hoped didn't sound as stupid to Red as it did to him) as his back hit one of the narrow support beams that were supposedly keeping the attic from collapsing in on itself. He felt a bruise form on one of his shoulder blades, blunt and uncomfortable and sure to be a bigger pain later than it was right at that moment.

 _This_ moment. On Valentine's Day.

Lust had read about it in some of the salvageable garbage that made it underground: it was a whole day that humans dedicated to love, and relationships. Pink was obsessed with it (so much so that he insisted on spending it all alone with Mettaton, but on the surface, with a reservation and a whole lot of other things that Geno and Paci had helped arrange for them -- Lust had to remember to pay them back at some point). Lust himself had only cared about it when he was younger (before It happened, and he stopped caring about a lot of things), and at this point in his life, after all he had done, he would have thought that having a date on an otherwise unassuming date (besides its name) would be meaningless to him.

Red gripped onto Lust's collar and yanked, making black leather slide against his cervical vertebrae and deform, pressing the embossed embroidery into his bones hard enough he could make out some of the letters. "s" and "a" were being rubbed deliciously close to the only scar on his body, making it hard to keep from moving even as Red pressed so close against him it made the sharper angles of his broken ribs dig against Lust's own through their clothes.

"yeah, slut, look't ya fuckin' _squirm_ ," Red sneered, voice heavy with gravel from years of smoking and screaming until he went hoarse. "ain't even done not'in' yet, 'n yer fuckin' _beggin'_ fer it."

Lust shifted his legs closer together, letting his skull fall back against the support beam with a hollow clack. His pants were far too tight, the ecto he had barely kept from forming downstairs now straining against the seams so hard he wasn't sure which would break first. Lust's shirt was riding up somehow, letting the lower of Red's broken ribs hooked against his own, grinding the fabric of Red's blood stained sweater through his intercostal spaces. Red's hand shifted, finally getting the tip of one of the letters sewn into Lust's collar to slide against the scar on his neck, sending a flair of the intent worked into the careful needlework burning through him like a grass fire in high summer. Lust moaned, sockets flickering shut, and when he was able to take another shaky breath, he could taste Red on the air: mustard, sweat, leather, nicotine and weed (the bitterness of Red's alcoholism faded with disuse, a sign of the progress he'd made, of how hard he was trying).

Lust's arms came up, his empty fingers twitching impotently in the air to either side of them both.

Red's dark chuckle sent another shiver down Lust's spine. "ain't so easy when its _yer_ blank check gettin' cashed, is it, pixie stick?"

"red, please-!!"

His answer was a tongue down his nonexistent throat, shoved harshly against his teeth until he bore it entrance, greeting it with his own. Red's smell was heady, but his taste wrung another moan from Lust. Mustard tried to cover it up, but without the harshness of Red's old boozing habits, the sweetness of watermelon washed over him with every hungry swipe of their conjured tongues.

If Lust hadn't already been told to keep his hands to himself this time ( _and that was fair -- Lust took charge so often, and his sweetheart deserved to have time when he felt strong and in control~_ ) he would have been clutching those smoke ruined clothes for dear life.

_He loved him so god damn much._

When Red pulled away, he was nearly twice as sweaty, face flushed a bright crimson to match what his eyelight had been a moment before. Two pure white pips stared back at him, taking him in. Lust knew how Red could feel what he felt ( _emotionally_ ) through the collar around Lust's neck. He _loved_ how flustered those feelings made Red.

"hands on me, but no funny business," Red mumbled.

Lust felt his insides go funny, bringing his hands in to cup Red's skull in one, and his spine in the other, guiding him back in closer, closer, yet closer for a softer, deeper kiss. Nobody would believe it from looking at him, but Red was _weak_ to gentle in ways that drove Lust absolutely crazy. Red liked _being_ rough, but liked getting it soft and slow and unhurried, lingering. Lust knew exactly how to kiss him back to make him feel that way.

Collar tight against his throat, drinking in his datemate's mewlings as he kissed him how he deserved, his hard-on near to bursting, Lust was the picture of decadence in his own humble opinion.

Then Red shoved him onto the lumpy mattress that had been left in the corner, climbing on top of him. Lust's bruised scapula ached in a soft burst at the impact, but that was nothing compared to the incessant, demanding throb between his legs. Red pinned Lust under him deliciously, sweetly, roughly pushing his clothes out of the way until there was enough of Lust's clavicle exposed to bite down on.

When Red came back up for another kiss, the taste of marrow and blood was added to the cocktail of flavors. Lust wouldn't change a damn thing.

"listenin', sweetheart?" Red's voice rumbled soft on his shaky exhale, still close enough for Lust to breathe back into himself. Lust grinned up at him, his magic pulsing needily at just hearing him say that innocent little petname back to him. After Lust nodded, Red leaned back. "i wanna do- i- fucker, just- gimme yer fuckin' SOUL!"

Lust felt his loose body go tight, the world going dark at the edges as every fear and anxiety and disappointment he still had left fought its way to the surface.

"fine, don't fuckin' bother," Red hissed, leaning back in to, presumably, bite him again.

As nice as that sounded ( _and it sounded very, very nice_ ), Lust caught Red's skull in both hands and held him back. "baby, wait-"

"wut fer?" Red demanded.

"why do ya wanna see my soul?"

Red clicked his teeth, avoiding direct eye contact. Neither one of them was the best at verbal communication, but Lust had been adamant about trying to improve that a little at a time. Lust liked to think they had both made significant improvements, but Red still struggled more often than not.

"...'s mine," Red finally muttered, his face dusted pink. "just want it. dun mean shit."

There was something painfully erotic about the admission. Lust's magic surged, and if he hadn't already ruined his pants before, he certainly had now. He shifted his hand over Red's cheek, cupping his face to pull him in for a kiss, reveling in the taste, in the feel of Red looming over him.

Lust already knew Red had seen his soul more than anyone else alive. Lust could feel it, like an after image, a lingering warmth after being touched: Red had held the culmination of his being in his hands. Lust couldn't remember it, but he knew. Lust didn't want whatever was wrong in his head to stop him from doing what he wanted with the man he loved.

Because he _did_ want to share that with Red, even if it was absolutely bat shit terrifying. Even if it was stupid and pointless and wouldn't amount to anything but a single moment shared. _He wanted it._

Lust wasn't going to think about that unattainable dream he had given up hope for a long time ago. He was going to think about what he _could_ do. And what he could do right at this moment was calm his ass down and let his boyfriend know how much love and trust he had in him.

"dun' get all sappy on me," Red grumbled, breathless after their kiss. Lust could hear it in his voice that whatever feedback he was getting was reassuring.

Lust tucked himself up close under Red's jaw, playing up their difference in size (even if it wasn't much bigger than the sole of a shoe) to make Red feel strong and important (which he was, in Lust's opinion). Red curled his arm around Lust, enveloping him in the miasma of Red's presence, leather and sweat and self medication. Lust panted, the party going on in his pants having never really let up, the heat of it starting to make him dizzy (especially with everything that turned him on being shoved in his face).

"if ya really wanna~, of course," Lust purred. "i'm yours~."

Red's arms tightened around him, holding Lust right where he wanted to be. A minute, two, just being held as Red played idly with the soft fringe of Lust's vest. The phantom of his touch near his neck had Lust hyper aware of every micro-motion, every quiver of his aching magic. Too soon, and yet not soon enough, Red let out a shaky huff and pulled Lust into a sitting position, maneuvering him so he was seated in Red's lap (the reverse of their usual, not that Lust minded being the little spoon every once in a while). Lust let him, more preoccupied with keeping his hands out of his own pants.

Once Red was sure of his own comfort, he growled at Lust. Lust pressed a kiss to his jaw, taking the hint. His one hand came up to his chest, rubbing a few little circles into his sternum before giving himself a sharp _tug_.

Lust's SOUL hovered gentle and unobtrusive, pearlescent white surface beaded in the purple of his magic and affliction. Lust didn't particularly like it, or see it as anything special (if anything, he hated showing it off). The only thing it appeared to be good for was causing trouble.

Red's claws came up to it, just short of touching. Lust was glad for the excuse not to see the disgust on Red's face.

"gonna... touch it right this time," Red rumbled low against Lust's acoustic meatus. His fingers didn't move a millimeter closer. It took Lust a moment of anticipation to realize that Red wasn't stating a fact so much as _asking permission_.

The genuine, fumbling attempts to try and communicate right had Lust's soul practically leap into Red's hands. "okay." Lust didn't care how ragged his own voice sounded.

He wanted to touch himself.

He wanted Red to touch him _more._

Red's fingers closed around the culmination of everything Lust had ever been, sharp claws coming to rest on the soft outer surface. Unwelcome _panic_ and _fear_ spiked at the sensation, memories of pain coming unbidden. Lust closed his sockets as if that would hide him from it, from the _absolutely unwelcome intruders_ to what was supposed to be a pure moment between him and Red.

"shhh.... i gotcha, sweetheart," Red rumbled again. One of his thumbs traced the crack that marred the surface of Lust's SOUL, paper thin and nearly unnoticeable if you weren't already looking for it. Lust felt every inch of it, felt the path traced with intent so potent it was making Lust dizzy and his hips buck up uselessly. "pisses me off, too."

Lust hadn't even realized he was angry to begin with. Leave it to Red to know that feeling better than anyone. _Lust loved him so fucking much._ He gripped the fabric of Red's shorts on either side of him, fisting the poor pantleg he was vaguely concerned he would rip. Red stroked in the opposite direction, and Lust moaned low and deep and vulnerable. It didn't feel like anything he could remember: not like the gentle platonic respect of his brother, assisting in a medical emergency; not like the cruel, uncaring dig of hands he never gave consent to. This was reverent, apologetic, spiritual. Lust felt _wanted_ , he felt _loved_ the way he had always wanted to be loved.

It was hard to tell what gushed first, his soul or his loins. All Lust could be certain of was that his lap was very, very wet, and his dick was still hard, and his cunt was regrettably still empty.

"fuck yeah..." Red sounded inordinately pleased, and when Lust looked, he could see Red's pulled one of his hands away to rub the lavender juice that was all over it between his fingers, thick silver liquid that Lust couldn't have suppressed if he tried mixing with his magic into a lewd, creamy purple pastel. "see what happens when yer a good pet? good shit happens. look't ya, came wit'out touchin' yerself once."

Lust wasn't normally into that sort of thing for himself, but the way Red called him a 'good pet' had his hips trembling all over again, wringing a whimper out of him.

Red returned his silver-slick hand back to Lust's soul, using both thumbs to make more forceful circles, sending wave after wave of pleasure through him. Lust sagged back into Red, trying to call his name but unable to make his useless tongue enunciate for him. His body jerked awkwardly, rhythmically, like Red was testing out a joystick to control his pelvis. More lavender oil pattered noisily onto Lust's lap.

All Lust could think about was how good it felt, how right, how perfect. All he could do was exist there, in Red's lap, in his arms, in his hands, exactly where he wanted to be, and take what he was given. All he could hear were his own ragged attempts at a voice, and Red's filthy little whispers, a comforting combination of genuine complements and vicious biting jabs.

"so fuckin' hot. look't ya. gonna cum again in my hand? filthy slut. not so tough now 're ya? hows it feel t' be 'n th' other side o' this shit? must feel pretty fuckin' good, how yer screamin'..."

Red's voice was starting to rip at the edges, the seams coming undone to leave him a bit ragged. It only made it more beautiful to Lust.

Red pulled one hand away again, lessening the overwhelming pleasure just enough for Lust to gather some coherency.

Any chance of a clear thought went out the window when Lust saw Red pull out his own SOUL. It was discolored with blackened callouses, splattered in cracks and fractures, pulsing with a crimson light that was desperately trying to cover up the soft green peaking through. Thick pastel pink and green tie dye ooze dribbled from its softer, porous patches.

Red hated being vulnerable. The very idea of it sent him into a state of panicked rage. He was the type to shoot first and ask questions never, because anything that kept him and his things (his people) safe was worth it. He could barely stand to show people his back at times.

There was only one reason he would bring his SOUL out at that moment. That reason was fraught with perils that Red was fully aware of (both academically and from personal experience). Yet, there he was, making himself the most vulnerable a monster could possibly be, _in front of Lust_ , for the singular purpose of sharing an experience with him.

Lust came to the very thought of it, shuddering and screaming with it, his SOUL exploding with shed magic. _He wanted it. He wanted him. So. Fucking. Much._

Red's purr vibrated against Lust's back through his ribs. "fuckin' hell. like that idea, eh?"

"please- please," Lust heard himself slur.

"fuck-!!" Red's voice swore against his neck.

Red's soiled hands brought the two inverted hearts closer, closer...

Until they touched. And then they weren't touching, because they were _one_.

Red was inside him, around him, a part of him.

Lust sobbed, so suddenly made to face everything Red was, all of his flaws, all of his virtues, all of _him_ , because, for this moment, they were Lust's too. There was too much to sort through, to categorize, to analyze and investigate, leaving Lust with only impressions: _ugly, hurt, scared, hatred, shame,_ but Lust was far too drawn to the _love_ , the _compassion_ , the _kindness_ that held everything together like a net of spiders silk, spiraling in on the singular _hope_ that Red was managing to hold onto. 

He loved him so much.

 _He_ loved _him_ so much.

There was a stifled, stuttering wet noise somewhere behind Lust, a hiccup, a whimper. Wetness and pressure against Lust's shoulders and back.

Red picked this position for a reason.

There must have been a few moments where Red's fingers went still; Lust slowly started to claw himself out of his cum drunk haze. He wanted to understand. He wanted to _know_. He wanted to revel in the decadence that was the culmination of his beloved's being.

He must have lingered too long focusing on just how _unfathomably compassionate_ Red could be, his kindness a precious jewel he kept locked away behind rotten walls, because the next thing Lust knew, the clasp of his belt buckle was undone and his dick was being pulled free of its leather confinement. Lust moaned in relief, rutting up into the slickened bones that were holding him so _fucking perfectly_.

Then both hands started to _move_ , talented fingers that had no business being as good as they were, working him into a lather, body and soul.

Lust was drowning. Lust was exactly where he wanted to be.

Red's claws grazed slow up Lust's length, scratching without scratching, lighting him up. Lust could feel it, the unspoken command/request/desire that he hold still and let Red work. Lust sobbed with the effort, but he had always had very good control of his body.

Red was pleased. Red was _happy_ and _awestruck_ and _horny as all fuck_. Lust shook as those perfect little claws grazed up to the tip of his dick, teasing the little hole. Red's other hand was working the flat of his thumb slowly, carefully, so as not to overwhelm Red as collateral damage. It was enough to warm up Lust's whole body, making him ache for Red's touch, to be kissed, to be bitten.

Red obliged, biting into Lust's shoulder from behind and _howling_ into his bones at how good he felt it felt for him. Lust's breath hitched, and he choked on a scream of his own. Red's hands still worked slow, achingly slow, blissfully slow. Lust couldn't see anymore, couldn't think anymore, all he could do was _feel_ and it was everything he ever wanted.

It was everything _he_ ever wanted, too.

If Lust hadn't already had tears in his eyes, the knowledge that this meant as much to Red as it did to himself would have brought them anyway.

Red's fingers worked faster, his own impatience and need winning out over the desire to draw out Lust's pleasure to its limit. The hand on Lust's dick switched from teasing distal tips to the slickened flats of his metacarpals, jerking him off wet and dirty, insistently, eagerly. Lust couldn't find where his own want and need ended and Red's began, a perfect, continuous loop of unmitigated gratification. _Yes. Yes. Yes yes yesyesyesyesyes-_

It felt too good. Lust was going crazy. Lust was driving _Red_ crazy and it was driving _him_ crazy.

The climax was explosive. Lust saw stars. He felt as if he were going to melt, or dust, or melt _then_ dust. It was too hot, too soft, too wet, too sudden, too _good_. Red was inside him and around him and holding him. He was _exactly where he wanted to be_ , and it was where Red wanted him to be too, and that made it even better.

_He loved him **so. Fucking. Much.**_

When Lust came back to himself, he was the little spoon as he and Red lay in an alarmingly large pool of slime, pastels mixing in a tie dye swirl, the edges drying in lewd silver. They were on their sides, Red's back to the wall as his arms held Lust tight against him. Their SOULs had unfused and returned to them, safe and sound. Their clothes were as close to ruined as they had ever been.

Lust had only felt this tired once in his entire life, and he had never felt this tired _and_ happy.

Red was breathing the deep, slow way he only did when he was sleeping peacefully, free of the nightmares and night terrors that haunted him when he was alone.

The room was much darker than it had been when he had been aware enough to see it last.

Lust fumbled blindly for his phone, shooting his brother a quick text that (hopefully) explained how he was okay, but he wouldn't be coming home for a while. Each movement reminded him that he had been bitten and thrown about, his shoulder and scapula lighting up in dull pain. Lust winced, deciding that it might be better for his bones if he lay on his other side. Wiggling with what little energy he had left to turn around (kicking off what was left of his pants in the process), Lust snuggled up against Red's chest, nuzzling a lipless kiss to his jaw before settling back in to return to sleep.

Red slept on, but his arms naturally adjusted to Lust's movement, curling to hold him close and secure, protective, possessive. Red's hands began to burn with magic, ameliorating intent seeping through to ease his aches to something more manageable. The echoes of the reason made Lust tear up all over again, overwhelmed by the emotional depth he had never dreamed of being prepare for, had never dreamed he would ever deserve.

He was exactly where he wanted to be.

It was a happy Valentine's Day.

**Author's Note:**

> This is officially my 33rd fic on AO3. -kazoo-
> 
> I'm happy to add more to the Resonance series (I'm calling it Resonantion for now, but it might change names later) since theres more I wanna do with this universe.
> 
> You could even say that this is a prologue of sorts. The beginning of the next big arch in the story.
> 
> Or you could say its trashy smut and i dunno what i'm doing XD


End file.
